R-T-B based sintered magnet

Abstract

An R-T-B based sintered magnet includes R 2 T 14 B crystal grains. A grain boundary formed by the two or more adjacent R 2 T 14 B crystal grains includes an R—N—O—C concentrated part having higher concentrations of “R”, N, O, and C than those in the R 2 T 14 B crystal grains. “R” of the R—N—O—C concentrated part includes Y. A ratio of Y atom to “R” atom in the R—N—O—C concentrated part is 0.65 or more and 1.00 or less. A ratio of O atom to “R” atom in the R—N—O—C concentrated part is more than 0 and 0.20 or less. A ratio of N atom to “R” atom in the R—N—O—C concentrated part is 0.03 or more and 0.15 or less.

The invention claimed is: 
     
       1. An R-T-B based sintered magnet comprising R 2 T 14 B crystal grains, wherein:
 “R” represents at least one rare earth element including Y, 
 “T” represents Fe or Fe and Co, 
 a grain boundary formed by the two or more adjacent R 2 T 14 B crystal grains includes an R—N—O—C concentrated part having higher concentrations of “R”, N, O, and C than those in the R 2 T 14 B crystal grains, 
 “R” of the R—N—O—C concentrated part includes Y, 
 a ratio of an average concentration of Y atom to an average concentration of “R” atom in the R—N—O—C concentrated part is 0.65 or more and 1.00 or less, 
 a ratio of an average concentration of O atom to the average concentration of “R” atom in the R—N—O—C concentrated part is more than 0 and 0.20 or less, 
 a ratio of an average concentration of N atom to the average concentration of “R” atom in the R—N—O—C concentrated part is 0.03 or more and 0.15 or less, and 
 an area ratio of the R—N—O—C concentrated part occupied in an area of the grain boundary on a cut surface of the R-T-B based sintered magnet is 0.20 or more and 0.75 or less.